Microstructures, such as microelectromechanical devices, have many applications in basic signal transduction. For example, a spatial light modulator based on a microelectromechanical device (MEMS) modulates light beams in response to electrical or optical signals. Such a modulator can be a part of a communication device or an information display. For example, micromirrors are key components of MEMS-based spatial light modulators. A typical MEMS-based spatial light modulator usually consists of an array of miniature reflective deflectable micromirrors. These micromirrors can be selectively deflected in response to electrostatic forces so as to reflect incident light by individual micromirrors for producing digital images. Such micromirrors, however, are sensitive to temperature and contamination, such as moisture and dust. This contamination has varying effects on the micromirrors, from capillary-condensation and post-release stiction to deterioration of the micromirror surfaces, which may result in mechanical failure of the micromirror devices in operation. For this and other reasons, micromirror devices are often packaged after releasing.
Regardless of differences of the packaging methods currently developed for a micromirror array device, two substrates, one for supporting the device and another one for covering the device, and sealing medium(s) for bonding the two substrates are utilized. Most of the sealing mediums require application of heat during bonding and sealing. The heat, however, may degrade the micromirror array device if not properly applied, especially for those microstructures and semiconductor devices that are temperature sensitive. For example, improperly applied heat may change the desired mechanical properties of the microstructures. It may also thermally activate particles, such as impurities and particles making up the functional components of the microstructures, prompting diffusion of these activated particles within the microstructures, thus exacerbating degradation of the microstructures. Or heat may decrease anti-stiction materials within the package.
Therefore, a method and an apparatus are needed for packaging microstructure, semiconductor, light emitting device, light modulating device, or light detecting device, particularly those that are temperature sensitive during packaging.